Yardsale does meet the description of "garage sale on the internet", but in the Craigslist sense more than the old-eBay sense: it's for selling stuff locally, not for selling worldwide and then shipping it. For some things that works fine, but for long-tail items with niche popularity I found the old ebay quite useful, because you could reach a non-geographically-constrained audience, increasing the odds that someone somewhere would want your obscure thing.

Nowadays I sell niche music and books on Amazon Marketplace, admittedly, so one chunk of that market is spoken for by a strong incumbent.